A vulnerability in Mitel 6900 Series IP (MiNet) phones excluding 6970, versions 1.8 (1.8.0.12) and earlier, could allow a unauthenticated attacker with physical access to the phone to gain root access due to insufficient access control for test functionality during system startup. A successful exploit could allow access to sensitive information and code execution.
packetstormsecurity.com/files/167547/Mitel-6800-6900-Series-SIP-Phones-Backdoor-Access.html
seclists.org/fulldisclosure/2022/Jun/32
www.mitel.com/support/security-advisories
www.mitel.com/support/security-advisories/mitel-product-security-advisory-22-0003
www.syss.de/pentest-blog/undocumented-functionality-backdoor-in-mitel-desk-phones-syss-2022-021